Influence of diffuser design on selected operating variables for wastewater flotation systems: a review

Air diffusers or spargers have since been used in separation processes that include conventional wastewater treatment. Over the years, there has been advancements in diffuser design in terms of shape, pore size, orientation and materials of construction as a way of mitigating challenges such as fouling, clogging, energy consumption and poor system efficiency. Some of the available air diffusers are inadequate to solve most of these challenges due to reduced quality and increased quantity of wastewater being treated. Additionally, there is a paucity of information regarding air diffuser design and their effect on operational parameters in wastewater treatment. This review seeks to address the advancement in diffuser design and also the effects of design factors including parameters of air diffusers with a focus of their use in a column flotation system for wastewater treatment.

The study of the column flotation capacities for stimulation of potash ore flotation

Potassium ore contains readily sludgable water-insoluble silicate–carbonate impurities which actively adsorb cation collectors (primary alkylamines) used in sylvine flotation. This fact determines inclusion of multistage de-sludging flowsheets, with rougher and cleaning flotation of sludge in the processing technology. A prerequisite for flotation de-sludging of ore is pre-flocculation of sludge. Flotation of sludge in mechanical flotation machines is carried out with intensive mechanical stirring of the suspension, which impairs the selective separation of sludge into the flotation froth and leads to the partial destruction of sludge floccules, which causes an increased consumption of the flocculant. In column machines, flotation is carried out in a laminar-upward flow of finely dispersed air bubbles ejected into the suspension in the lower part of the column, and is characterized by the minimal hydromechanical effect on the mineral particle–air bubble attachment. An important feature of flotation in column machines is the adjustability of the foam layer height in a wide range of values (up to 0.5 m and more) and its washability, which makes it possible to increase the recovery selectivity of the floated material into the foam product. The design of column machines for enrichment of potash ores, which are water-soluble and floatable in rich salt solutions, should ensure elimination of crystallization of the aeration system for supplying air to the column machine. The tests of column flotation of sludge produced from potash ores of the Upper Kama deposit with different contents of water-insoluble impurities were carried out on the experimental installation of ERIEZ Flotation Division. The results of the comparison of flotation efficiency and selectivity in mechanical and column flotation machines are presented. The possibility of de-sludge flotation of potash ores with different contents of water-insoluble impurities (1.5–4%) with the significant improvement of flotation selectivity at the lower consumption of reagents is shown. The use of column flotation creates conditions for simplifying the instrumental and technological flowsheet of flotation.

Flocculation as an Alternative to Increase the Recovery of Ultrafine Particles of Pyrite in Flotation of Tailings

<p>Nowadays, flotation is the most commonly used method for mineral concentration. However, conventional flotation circuits are not suitable for ultrafine particles, and this is a challenge for the concentration of finely disseminated minerals. Moreover, tailing contain a considerable amount of very fine particles which can include valuable and hazardous minerals that have the potential to be recovered. Concern about ultrafine particles has increased as they are present in a wide variety of mineral pulps and can contain valuable minerals that have been lost to the tailings. Several alternatives have been proposed to improve the recovery of ultrafine particles in flotation, for example, decreasing the size of the air bubbles, column flotation, selective agglomeration of particles, etc. Among all, selective polymeric flocculation represents a promising option. The current study focuses on the use of polymeric flocculation to increasing the size of pyrite particles aiming to improve its recovery in the flotation of sulfidic tailings. Flocculation was performed with pyrite particles presenting P80 < 4 mm, in aqueous medium and alkaline conditions. Two polyacrylamides and a new nanocellulose-based chemical were used as flocculants. Microflotation tests were performed, without the addition of collector, to evaluate the formation of flocs through the reduction of the mechanical entrainment of pyrite after being submitted to flocculation.</p>